Bab 08 QoS Tambahan

7/30/2019 Bab 08 QoS Tambahan

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Introduction to

Quality of Service

Ir. Gunawan Wibisono, M.Sc, Ph.D

Klara Nahrstedt


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Outline

Requirements on Multimedia

Communication and Operating Systems

Real-time and multimedia

Resource management

Resources

Quality of Service (QoS) Concept

Operations

CS 414 - Spring 2008


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Requirements

Resource management resourcereservation/allocation/adaptation

Transport system guaranteed deliverywith respect to metrics such as delay,

reliability, bandwidth requirements

Process management real-timeprocessing of continuous data,

communication and synchronization

between processes/threadsCS 414 - Spring 2008


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Requirements (2)

Memory/Buffer management guaranteedtiming delay and efficient data

manipulation File system/Media Servers transparent

and guaranteed continuous retrieval of

audio/video Device management integration of audio

and video



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Resources Classification

Resource is a system entity required by

tasks for manipulating data

Active versus Passive Resources (CPUactive; main memory passive)

Shared versus Exclusive Resources (CPU

shared; audio device exclusive) Single Versus Multiple Resources (single

CPU in PC, multiple CPU in multi-core

systemCS 414 - Spring 2008


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Real-Time and Deadlines

Real-time system system in whichcorrectness of computation depends not

only on obtaining the right results, but alsoproviding them on time

Examples: control of temperature in a

chemical plant; control of a flight simulator

Deadline represents the latestacceptable time for the result delivery

Soft deadlines versus hard deadlines



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Real-Time and Multimedia

Difference between RT requirements for

traditional RT systems and Multimedia

systems

Fault tolerance and security

Soft deadlines versus hard deadlines

Periodic behavior versus random behavior

Bandwidth requirements



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Resource Management (Why do

we need resource management?) Limited capacity in digital distributed

systems despite data compression and

usage of new technologies Need adherence for processing of

continuous data by every hardware and

software component along the data path Competition for resources exist in an

integrated multimedia system



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Window of Insufficient

Resources



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Layered Partition of Multimedia Systems with

respect to Required Resources and Individual

Services



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Quality of Service MM systems consist of set of services

To provide generic MM services, services get

parameterized with so called Quality of Service

Examples of QoS parameters:

QoS for Audio service:

Sample rate 8000 samples/second

Sample resolution 8 bits per sampleQoS for network service:

Throughput 100 Mbps

Connection setup time 50 msCS 414 - Spring 2008


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QoS (cont.)

QoS concept comes from networking service

and was introduced for specification how good

the offered network services are

Services are performed on different objectsMedia sources

Media sinks

Connections

QoS specification characterizes the

service objects



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Layered Model for QoS



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Application QoS Parameters



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System QoS Parameters



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Network QoS Parameters



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QoS Classes

Guaranteed Service Class

QoS guarantees are provided based on

deterministic and statistical QoS parameters

Predictive Service Class

QoS parameter values are estimated and

based on the past behavior of the service

Best Effort Service Class

There are no guarantees or only partial

guarantees are provided



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QoS Classes (cont.)


QoS Class determines: (a) reliability of offered QoS, (b) utilization of resources


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Single Value: QoS1 average (QoSave),contractual value, threshold value, target value

Pair Value: with

QoS1 required value; QoS2 desired valueExample: ;


Deterministic QoS Parameters


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Deterministic QoS Parameter

Values Triple of Values

QoS1 best value

QoS2 average value

QoS3 worst value

Example:

, where QoS isnetwork bandwidth



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Guaranteed QoS We need to provide 100% guarantees for QoS values

(hard guarantees) or very close to 100% (soft

guarantees)

Current QoS calculation and resource allocation are

based on:1. Hard upper bounds for imposed workloads

2. Worst case assumptions about system behavior

1. Advantages: QoS guarantees are satisfied even in the

worst case case (high reliability in guarantees)2. Disadvantage: Over-reservation of resources, hence

needless rejection of requests



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Predictive QoS Parameters

We utilize QoS values (QoS1, ..QoSi) and

compute average

QoSboundstep at K>iis QoSK= 1/i*jQoSj

Weutilize QoS values (QoS1, , QoSi) and

compute maximum value

QoSK= maxj=1,i(QoSj)

We utilize QoS values (QoS1, , QoSi) and

compute minimum value

QoSK= min j=1,i(QoSj)CS 414 - Spring 2008


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Best Effort QoS

No QoS bounds or possible very weak

QoS bounds

Advantages: resource capacities can bestatistically multiplexed, hence more

processing requests can be granted

Disadvantages: QoS may be temporallyviolated



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Quality-aware Service Model Quality-aware Autonomous Single Service

Consists of a set of functions

Accepts input data with QoS level QoSin

QoSin=[q1in,..qn

in]

Generates output data with QoS level QoSout

QoSout=[q1out,..qn

out]

Example: Video player service

Input QoS: [Recorded Video Frame Rate, Recorded Frame Size,

Recorded Pixel Precision] QoSin=[30fps, 640x480 pixels, 24 bits per pixel]

Output QoS: [Playback Video Frame Rate, Playback Frame

Size, Playback Pixel Precision]

QoSout=[20fps, 320x240pixels, 24bits per pixel]



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Quality-aware Service Model Quality-aware Composite Service

Consists of set of autonomous services that are connected into a

directed acyclic graph, called service graph

Is correct if the inter-service satisfied the following relation:

QoSoutof Service K satisfies QoSin of Service Miff qKj

out= qMlinforqMl

in being single QoS value

qKjout is in qMl

inforqMlinbeing a range of QoS value

Example:

Video-on-demand service, consists of two services: retrieval

service and playback service Output quality of the retrieval service needs to correspond to input quality of

playback service, or at least falls into the range of input quality of playback

service



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Relation between QoS and

Resources



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Operations on QoS in Phase 1

(Translations) Layered Translation of QoS parameters

(must be bidirectional)

Human (user QoS) application QoSApplication QoS system QoS

System QoS network QoS

Media ScalingTransparent scaling

Non-transparent scaling



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Layered Translation (Example)



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Media Scaling (Examples)

Audio

Transparent scaling difficult (one hears the

quantization noise)Non-transparent scaling should be used

Video

Temporal scalingSpatial scaling

Color space scaling (reduction of number of

entries in color space)CS 414 - Spring 2008


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Conclusion

QoS an important concept in multimediasystems

Very different types of QoS parametersand values

Important relation between QoS and

Resources Need to understand operations on QoS

and their impact on resource management



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Outline

Requirements on Multimedia

Communication and Operating System

Real-time and multimedia

Resource management

Resources

Quality of Service (QoS) Concept

Operations



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Resources



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Phase 1: Establishment Phase(QoS Operations)


QoS Translation at different Layers

User-Application

Application-OS/Transport Subsystem

QoS Negotiation

Negotiation of QoS parameters among two

peers/components

QoS Routing along the end-to-end path


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QoS Operations within

Establishment Phase


User/Application

QoS Translation

Overlay P2P

QoS Negotiation

Application/Transport

QoS Translation

QoS Negotiation/

QoS Routing in

Transport Subsystem


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Operations on QoS in Phase 1

(QoS Translations) Layered Translation of QoS parameters

(must be bidirectional)

Human (user QoS) application QoSApplication QoS system QoS

System QoS network QoS

Media ScalingTransparent scaling

Non-transparent scaling



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Media Scaling (Examples)

Audio

Transparent scaling difficult (one hears the

quantization noise)Non-transparent scaling should be used

Video

Temporal scalingSpatial scaling

Color space scaling (reduction of number of

entries in color space)CS 414 - Spring 2008


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QoS Negotiation



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Different Types of Negotiation

Protocols Bilateral Peer-to-Peer Negotiation

Negotiation of QoS parameters between

equal peers in the same layer Triangular Negotiation


layers

Triangular Negotiation with Bounded

Value



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Bilateral QoS Negotiation



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Triangular QoS Negotiation



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Triangular Negotiation with

Bounded Value



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QoS Routing


1G

10G

200 M

10G 2G

100M

2G

100M

2G

10G 10G

2G

1G = 1Gbps

10G = 10 Gbps

100 M = 100 Mbps

End Node

Network Router

Node ANode B


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QoS Routing


1G

10G

200 M

10G 2G

100M

2G

100M

2G

10G 10G

2G

1G = 1Gbps

10G = 10 Gbps

100 M = 100 Mbps

If QoS Request on a connection

from Node A to B is 150 Mbps, the

QoS Routing question is

-Does a route from A to B exist that

satisfies the QoS requirement?- What is the best route?

Node A

Node B

End Node

Network Router


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QoS Routing

Performed during establishment phasemostly, but also during transmission phase

to adapt a route if needed

Need to discover route (path) that meetsQoS requirements such as throughput,

end-to-end delay, loss rate

End-to-end Throughput is a min-based metricEnd-to-end Delay is additive metric



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Unicast QoS Routing

Problem Formulation:Given a source node A, destination B, a set of QoS

constraints C, and possibly an optimization goal, we

aim to find the best feasible path from A to B which

satisfies C. Bandwidth-optimization problem: to find a path that has the largest

bandwidth on the bottleneck link (widest path)

Bandwidth-constrained problem: to find a path whose bottleneck

bandwidth is above a required threshold value

Delay-optimized problem: to find a path whose total delay is

minimized

Delay-constrained problem: to find a path whose delay is bounded

by a required value.



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QoS Routing Strategies

Source Routing Each node maintains global state and feasible path is locally

computed at the source node

Distributed Routing Control messages exchanged among nodes and the state

information kept at each node is collectively used for the path

search

Hierarchical Routing Nodes are clustered into groups creating multi-level hierarchy One can use source routing within a cluster and distributed

routing among clusters



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Multimedia Resource Management

Resource managers with operations andresource management protocols

Various operations must be performed by resource

managers in order to provide QoS

Establishment Phase Operations are executed where schedulable units utilizing

shared resources must be admitted, reserved and allocated

according to QoS requirements

Enforcement Phase Operations are executed where reservations and allocations

must be enforced, and adapted if needed



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Establishment Phase Operations

QoS to Resource MappingNeed translation profiles

Resource Admission

Need admission tests to check availability ofshared resources

Resource Reservation

Need reservation mechanisms along the end-to-end path to keep information about reservations

Resource Allocation



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Continuous Media Resource Model

One possible resource utilization model formultimedia data Linear Bounded ArrivalProcess Model (LBAP)

LBAP models message arrival process:M maximum message size (in bytes)

R maximum message rate in messages per

secondB maximum burstiness (accumulation of

messages)



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LBAP Resource Model

If we have (M,R,B), we can predict

utilization of resources:

Maximum numberNof messages arriving atthe resource: N = B + R x TimeInterval

Maximal Average Rate R (in bytes per

second): R = M x R

Maximal Buffer Size (BS in bytes): BS = M x

(B+1)



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Example of LBAP

Consider M = 1176 Bytes per message, R = 75

messages per second, B = 10 messages

During a time interval of 1 second, the maximum number

of messages arriving at a resource must not exceed N =

10 messages + (75 messages/second * 1 second) = 85

messages

Maximum average data rate in bytes per second is R =1176 bytes * 10 messages/second = 88200

bytes/second

Maximum buffer size in bytes in BS = 1176 bytes * (10

messages + 1) = 12936 bytes



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Admission Tests

Task schedulability tests for CPUs This is done for delay guarantees

Packet schedulability tests for sharing host

interfaces, switches This is done for delay and jitter guarantees

Spatial tests for buffer allocation

This is done for delay and reliability guarantees

Link bandwidth tests

This is done for throughput guarantees



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Resource Reservation and Allocation

Two types of reservations Pessimistic approach - Worst case reservation of resources

Optimistic approach -Average case reservation of resources

To implement resource reservation we need:

Resource table

to capture information about managed table (e.g., process

management PID table)

Reservation table

to capture reservation information

Reservation function

to map QoS to resources and operate over reservation table



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Two types of reservation styles:

Sender-initiated reservation

Receiver-initiated reservation


C d A t f M lti di


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Covered Aspects of Multimedia

Image/VideoCapture

Media

Server

Storage

Transmission

Compression

Processing

Audio/Video

PresentationPlaybackAudio/Video

Perception/

Playback

Audio Information

Representation

Transmission

AudioCapture

A/V

Playback

Image/Video Information

Representation



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Multimedia System/Network


Network

MM

Application

OS/DS/Network

MM

Application

OS/DS/Network

Sender Receiver


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Resources (Phase 1)


Translation,

Negotiation

Admission,Reservation


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Phase 1: Establishment Phase(QoS Operations)


QoS Translation at different Layers

User-Application

Application-OS/Transport Subsystem

QoS Negotiation

Negotiation of QoS parameters among two

peers/components


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Phase 1: Connection Establishment


Network

MM

Application

OS/DS/Network

MM

Application

OS/DS/Network

Sender Receiver

Translation

Logical Negotiation ofNetwork QoS Parameters

Physical Transmission of

Negotiation Parameters

Logical Negotiation of

Application QoS Parameters


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QoS Operations within

Establishment Phase


User/Application

QoS Translation

Overlay P2P

QoS Negotiation

Application/Transport

QoS Translation

QoS Negotiation in

Transport Subsystem


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Example

Video Stream Quality:

Frame size: 320x240 pixels, 24 bits (3 Bytes

per pixel)

Application frame rate RA: 20 fps

Translate to Network QoS if

Assume network packet size is 4KBytes

Network packet rate (RN):= 320x240x3x20bytes / 4096 bytes



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QoS Negotiation



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Different Types of Negotiation

Protocols Bilateral Peer-to-Peer Negotiation


equal peers in the same layer

Triangular Negotiation


layers

Triangular Negotiation with Bounded

Value



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Bilateral QoS Negotiation



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Triangular QoS Negotiation



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Triangular Negotiation with

Bounded Value



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Triangular Negotiation Protocol (Pseudo-Code Example)


Caller Callee

Network-Service Provider Pseudo-Code

Caller Pseudo-Code

Callee Pseudo-Code


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Multimedia Resource Management

Resource managers with operations andresource management protocols

Various operations must be performed by resource

managers in order to provide QoS

Phase 1: Establishment Phase (resource

operations) Operations are executed where schedulable units utilizing

shared resources must be admitted, reserved and allocatedaccording to QoS requirements

Phase 2: Enforcement Phase Operations are executed where reservations and allocations

must be enforced, and adapted if neededCS 414 - Spring 2012


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Phase 1: Resource Preparation Operations

QoS to Resource Mapping

Need translation or profiling (e.g., how much

processing CPU cycles, i.e., processing time, it

takes to process 320x240 pixel video frame)

Resource AdmissionNeed admission tests to check availability of

shared resources

Resource ReservationNeed reservation mechanisms along the end-to-

end path to keep information about reservations

Resource AllocationCS 414 - Spring 2012


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Phase 1: Connection Establishment


Network

MM

Application

OS/DS/Network

MM

Application

OS/DS/Network

Sender Receiver

Translation

Logical Negotiation of NetQoS Parameters


Negotiation Parameters

Network Resource

Reservation Protocol NetworkResource

Admission and


System

Resource

Admission and

Reservation

Logical Negotiation of App

QoS Parameters


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Admission Tests

Task (System) schedulability tests for CPU

resources This is done for delay guarantees

Network Packet schedulability tests for sharing hostnetwork interfaces, network switches This is done for network delay and jitter guarantees

Spatial tests for memory/buffer allocation

This is done for delay and reliability guarantees

Network Link bandwidth tests

This is done for network throughput guarantees



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Resource Reservation and Allocation

Two types of reservations Pessimistic approach - Worst case reservation of resources

Optimistic approach -Average case reservation of resources

To implement resource reservation we need:

Resource table

to capture information about managed table (e.g., process

management PID table)

Reservation table

to capture reservation information

Reservation function

to map QoS to resources and operate over reservation table



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Two types of reservation styles:

Sender-initiated reservation

Receiver-initiated reservation


R l ti b t Q S d


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Resources (Phase 2)


Translation,

Negotiation

Admission,Reservation

Scheduling,

Rate Control,

Error ControlFlow Control

QoS ManagementCompression

Phase 2: Media Processing and


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Phase 2: Media Processing and

Transmission


Network

MM

Application

OS/DS/Network

MM

Application

OS/DS/Network

Sender Receiver


Media

Network

Resource

Scheduling

System

Resource

SchedulingRate Control

Flow Control

Error

Control


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Phase 2: Enforcement Operations

Resource scheduling

Example: rate-monotonic scheduling

Rate control traffic shaping Example: leaky bucket

End-to-end error control

Example: forward error correction

Flow controlOpen loop flow control (no feedback)

Close look flow control (with feedback channel)


Q S


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QoS Management during

Transmission Phase

Resource and QoS Monitoring

Flexibility, i.e., monitoring should be turned on/off

Two types of monitoring User-mode monitoring

Network-mode monitoring

QoS Maintenance

Compares monitored QoS with contract QoS QoS Degradation

graceful degradation needed


Q S M d i


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QoS Management during

Transmission Phase

QoS Renegotiation and Signaling

In case QoS parameters need to change,

renegotiation must be initiated QoS/Resource Adaptation

As a result of re-negotiation request (request

for change in quality) adaptation in QoS and

resource allocation must happen



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QoS/Resource Adaptation

Renegotiation request can come from

User

Host systemNetwork

Resource adaptation

Network adaptation (e.g., dynamic re-routingmechanism)

Source adaptation (e.g., temporal scaling with

feedback)CS 414 - Spring 2012

R D ll ti T


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Resource De-allocation Tear-

Down Phase Reserved Resource must be freed up

once multimedia session is over

Tear-down processSender-initiated closing (release reservation)

Receiver-initiated closing (release

reservation)



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Conclusion Current State of Art

Lack of mechanisms to support QoS

guarantees

Need research in distributed control,

monitoring, adaptation and maintenance of

QoS mechanisms

Lack of overall frameworks

Need QoS frameworks for heterogeneousenvironments (diverse networks, diverse

devices, diverse OS)

Bab 08 QoS Tambahan

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